The paper does not analyze the transactions directly unless I'm missing that piece. There are a number of reasons accounts would interact with the scam tokens such as the scamming group filling up the liquidity pool, creating fake volume to add legitimacy, and other steps to complete the scam.

There's also the obvious case of the scammers getting a user to actually buy the token (perhaps through spam email or "pump groups" that give explicit instructions on how to perform the swap) which I'm not saying has never happened but I do claim is more rare. Even the obviously silly scam emails do have the occasional person click on them and lose their money. The upside is that getting scammed on Uniswap is actually harder as you need to manually bypass safety features.